Blowout control valve for drilling well



A ril 28, 1970 R. P. VINCENT ET 3,503,577

BLOWOUT CONTROL VALVE FOR DRILLING WELL Filed April 5. 1967 2 Sheets-Sheet 1 FIG. 4

INVENTORS RENEC P. VINCENT BYBILLY v. RANDALL ATTORNEY April 28, 1970 R. P. VINCENT ET AL 3,508,577

BLOWOUT CONTROL VALVE FOR DRILLING WELL Filed April 5, 1967 2 Sheets-Sheet 2 P a: "I

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QZfiM ATTORNEY United States Patent 3,508,577 BLOWOUT CONTROL VALVE FOR DRILLING WELL Renic P. Vincent and Billy V. Randall, Tulsa, Okla, assignors to Pan American Petroleum Corporation, Tulsa, Okla, a corporation of Delaware Filed Apr. 5, 1967, Ser. No. 628,747 Int. Cl. Flfik 29/02 U.S. Cl. 137528 2 Claims ABSTRACT OF THE DISCLOSURE A backpressure control valve is disclosed. A conventional automatic blowout control system for a drilling well includes a conventional blowout preventer connected into the well casing system and a conduit connected to the casing below the conventional blowout preventer. The automatic backpressure control valve of this disclosure is connected into this conduit. The backpressure control valve includes a housing having a longitudinal bore or passage therein and an outlet bore which is at 90 to the main bore. A piston valve means having a wedge-shaped tungsten carbide face, preferably at 45 angles, is mounted in the valve body and axially aligned within the main bore. Hydraulic fluid under controlled pressure forces the piston valve to a closed position. When the pressure in the intake to the valve body exceeds this controlled pressure, the piston valve is forced open. The slanting face of the valve provides for rapid passage of any accumulated cuttings when the valve is open and eliminates sticking problems due to such cuttings. In one embodimerit, a special carbide deflecting ring is provided about the piston valve. Other embodiments include piston centralizing means and means to rotate the piston valve during operations to distribute wear.

This invention relates to a control system for use in drilling wells. It relates especially to a novel fluid control valve for use in controlling the backpressure of the drilling fluid used in such drilling wells.

BACKGROUND When drilling oil and gas wells by the rotary drilling method, a bit is attached to the lower end of a string of hollow drill pipe and the bit normally obtains its rotation by rotation of the drill pipe at the surface.

Drilling fluid is circulated normally down the drill pipe, through the bit and up the annulus between the drill pipe and the borehole wall. The drilling fluid is used primarily to remove cuttings made by the bit and to lubricate and cool the bit. When a liquid is used as the drilling fluid, the hydrostatic head of this liquid outside the drill pipe imposes a pressure on the formation which is highest at the bottom of the well. In some cases the drilling formation contains a gas, a liquid or a mixture of gas and liquid at a pressure greater than this hydrostatic head. When the bit reaches such a formation, the high pressure fluid enters the well and flows toward the surface with the drilling fluid outside the drill pipe. The fluid entering the well may be salt water, oil or natural gas. Oil and gas are almost always less dense than the circulated liquid drilling fluid. If the circulated drilling fluid has been weighted with the addition of suspended particles, e.g., barite, as is usually the case, even salt water is less dense than such drilling fluid. If these less dense fluids dilute the heavier drilling fluid, the hydrostatic pressure is reduced and still more fluids enter the well bore from the formation. This process can continue until the well is flowing. One ordinarily does not want a well to flow during drilling operations.

In order to regain control of the well, a blowout preventer, which is a means of closing the upper end of the casing, may be closed. Normally, this means sealing the annular space between the drill pipe and the casing. The blowout preventer may be closed while a more highly weighted drilling fluid is circulated down the drill pipe. In order to fill the annular space between the drill string and the well wall with this heavier liquid, it is necessary to allow some flow from the well below the blowout preventers. It is customary to provide a choke valve on a flow line from the casing below the blowout preventer. Fluids can be bled oil? through this choke, permitting the more highly weighted drilling fluid to be circulated up the well outside the drillpipe. The choke valve must hold back pressure on the top of the well to restrict flow of the high pressure formation fluids into the well.

The highly restricted flow through the choke valve has several very detrimental effects. Three of the more undesirable effects are: (l) The rate of circulation of liquids through the well is greatly reduced. (2) The choke, which is essentially a fixed orifice, is extremely sensitive to fluid flow rate because the pressure drop across the unit varies as the square of the flow rate. (3) The choke valve frequently is plugged by the bit cuttings, lost circulation materials and the like. These problems result in pressure surges which occur until the mud pumps can be shut down. Such surges can easily fracture drilling formations, resulting in serious lost circulation problems.

Various of these and other problems are discussed in more detail in articles in the Oil and Gas Journals, Sept. 10, 1962, p. 106, and June 28, 1964, p. 52. Various solutions of these problems have been suggested. One such system is described in US. patent application Ser. No. 430,918, filed Feb. 8, 1965, now Patent No. 3,354,970 and assigned to a common assignee to this application. It provides a long-lasting, simple, automatic apparatus for holding backpressure on the well outside the drill pipe While permitting high rates of drilling fluid circulation and minimizing the danger of high pressure surges. More specifically, it replaces the choke in the choke line with a specially designed valve. Regan Forge and Engineering Company, San Pedro, Calif., supplies an automatic backpressure control (ABC) valve such as described in said application. This valve has proved quite useful. That valve includes a rubber sleeve which closes about a mandrel upon applying pressure to the exterior of the sleeve. The present invention provides an alternate to the above-mentioned automatic control valve in the choke line and employs no rubber sleeve.

BRIEF DESCRIPTION OF THE INVENTION In a preferred embodiment, the valve includes a body in the form of a modified pipe T which has a hard metal ring set in one opening of the main bore of the T. A piston valve having a hard metal end of the same diameter as the hard metal seat is provided in the main bore with the hard metal end facing the hard metal seat. The face of the hard metal end of the piston has a wedge-shaped surface. Controlled hydraulic fluid is maintained at the desired pressure on the end of the piston opposite the hard metal head. The piston valve is opened when the pressure of the fluid such as drilling mud in the first opening of the T exceeds the controlled pressure. The mud flows out a bore which intersects the main bore of the housing intermediate the ends thereof.

DESCRIPTION OF THE DRAWINGS Various objects and a better understanding of the invention can be had from the following discussion taken in conjunction with the drawings in which:

FIG. 1 illustrates the assembly of our flow control valve into well head equipment;

FIG. 2 illustrates a cross-section of one embodiment of our invention;

FIG. 3 illustrates a modification of the flow control valve of FIG. 2;

FIG. 4 illustrates another embodiment of ourflow control valve; and

FIG. 5 is a section taken along the line 5-5 of FIG. 4.

FIG. 1 illustrates how our flow control valve is used in conjunction with the well casing and blowout preventer. Shown thereon is a casing which extends into a well bore and has been cemented therein. Mounted on casing 10 is a blowout preventer 12. A drill pipe 14 extends downwardly through blowout preventer 12 and casing 10 to the bottom of the well bore. Ordinarily, blowout preventer 12 is a type which can seal or close off the annular space between the drill pipe 14 and the housing of the blowout preventer when actuated. Such equipment is well known and will not be discussed futher here. Below blowout preventer 12 there are two openings into casing 10. These are openings 16 and 18. Conduits 20 and 22 having valves 24 and 26 connect into openings 16 and 18, respectively. Conduit 20 is used in a conventional manner and is called a fill line and is used to pump mud into the well bore, and may or may not be used at the time the preventer is closed. Cur flow control valve 28 is connected to choke line 22. Control fluid is provided through control line 30 to the control valve 28. Flow control valve 28 is used to control the pressure within casing 10.

Attention is now directed toward FIG. 2 which illustrates in cross-section a preferred embodiment of our flow control valve. Shown thereon is a housing 32 which has openings in the shape of a T. A longitudinal bore has a first opening 34 and an opposite opening 36. A third opening 38 is at right angles to the bore of the other two openings. A first nipple 40 is threadably (or otherwise) connected into opening 34 of housing 32. The end of nipple 40 which is provided with ring 42 is inserted into the housing and is made of a hard metal such as tungsten carbide. This preferably takes the shape of a ring and forms the seat of the valve. A piston 44, having the same diameter as the internal diameter of ring 42 is inserted in opening 36 which is opposite the opening in which ring 42 is mounted. Piston valve 44 is cylindrical in shape, i.e., having the same diameter along that part which may be in contact with the drilling fluid. This aids in preventing any accumulation of cuttings from interfering with the longitudinal movement of valve piston 44. Also, the opening and closing of the valve is not influenced by any back pressure of fluid in communication with outlet 38.

A nipple forming a cylinder means 46 for piston 44 is threadably or otherwise connected into opening 36 of valve housing 32. Seals 48 are provided in cylinder means 46 to form a sliding and sealing contact with piston 44. The end of piston 44 which extends into seat 42 is provided with a hard metal head 50 which is preferably made of tungsten carbide. The end of piston valve 44 opposite the head 50 extends into a pressure chamber 52 which is formed between the piston and an end plug 54. Hydraulic control fluid is provided through line 56. The portion of piston 44 which is of enlarged diameter and is in chamber 52 acts as a stop and this enlarged portion has a non-sealing surface or relationship with the interior of nipple 46 and with shoulder 47.

It will be noted that the ends of nipples 40 and 46 are spaced apart. Thus, there is clearance around valve piston 44 between nipples 40 and 46. Mounted in this clearance space about piston 44 is hard metal deflector ring 58 which is used to deflect fluid, particularly away from seals 48. The fluid flows out through opening 38 which is provided with nipple 60. Body 32 is also preferably lined with abrasion resistant material (as illustrated at 97 in FIG. 4, for example) to prevent damage from the high velocity fluid jet when the valve is opened. When valve head 50 first opens there is considerable jet action caused 4 by the rapid flow of fluid between seat 42 and head 50. This jet action is directed toward carbide rings 58, or against a carbide lining of the valve, and thus prevents the jet action abrading the valve body itself.

Valve head 50 is wedge shaped. It is preferred that the face of head 50 be formed of two planes and that each plane make an angle of with the axis of piston 44 as also shown in FIGS. 3 and 4. By making the face of valve head wedge shaped, one prevents sticking of the piston 44 due to side thrust if the head was only cut at one plane. Further, by making the valve head 50 wedge shaped, one is able to obtain much closer backpressure control. An axial movement of piston 44 away from ring 42 has an initial area of small dimensions as only that portion of the circumference of the valve head which is cut by the planes of the wedge is opened at first. Even closer backpressure control can be obtained if the face of valve piston 44 is formed by only one plane; then the face would be as indicated to include dashed extension 50A. (The preferred embodiment does not include extension 50A.) If this side thrust becomes too great a problem in high flow rates, the angle could be increased above 45 to about to reduce the side thrust. By making the face wedge shape, i.e., of two planes as in the preferred embodiment, one can effectively avoid the side thrust problem. The angle which a cutting plane makes with the axis of piston 44 should not be over about 60. The angle shown in the drawing is about 45. For purposes herein the face of the head 50 can be called chisel shaped, whether made of one or more planes. If the face of valve head 50 was a plane perpendicular to the piston, the entire circumference would be opened when the valve is moved from ring 42. This would reduce the sensitivity of backpressure control.

In operation, control fluid is provided through conduit 56 to chamber 52. The pressure in this control line is the pressure which it is desired to maintain in the annulus of the well casing. When the pressure P in nipple 40 exceeds the pressure in chamber 52, piston 44 is pushed to the right to an open position. As just explained, the valve has a wide range of opening area as the valve is moved to the right. This permits a close control of the pressure P in pipe 40. As the pressure P increases beyond the pressure in chamber 52, the valve opens, thus relieving pressure P. Sometimes cuttings 62 may accumulate and as the valve starts to open these cuttings may tend to restrict the flow and cause a slight rise in the mud pressure P being restrained. This increased pressure P in turn causes the piston valve 44 to move further to the right allowing the cuttings to flow more easily toward opening 38. Thus, the valve is self-purging. Cuttings accumulating as shown can cause a part of the pressure drop and the washing action of the mud through the cuttings will abrade them away. It is to be further noted that in this embodiment, the valve opening can be as large as a pipe 40 through which the mud enters the valve. This makes it impossible to bridge the opening.

Attention is next directed to FIG. 3 which shows a modification of the device of FIG. 2. This shows means for rotating the piston 44 and the head 50. It is desired to rotate the piston as this will spread the cutting action of the mud stream on the hard metal ring 42, thus prolonging the valve life. The valve is modified to include a shaft 64 which extends out end 66. Shaft 64 can be rotated either manually at frequent intervals or continuously by use of a motor 68 connected through clutch '70 to shaft 64. If the device is altered to have a shaft 64, then it is also altered so that the driven end 70 of piston 44A has an area A exceeding the cross-sectional area A of shaft 64 which is equal to the cross-sectional area A of the piston 44A upon which the lateral force of the mud acts. Thus, A=A A Nipple 46A is screwed into opening 36 of the valve body and has a stepped internal bore. A part 46B of the bore has a diameter equal to the diameter of piston portion 44A and a second part 46C equal to the diameter of enlarged piston portion 72. Cylinder 46A has a port 74 to prevent buildup of pressure in annular space 76 between the smaller portion of piston 44A and cylinder 46A. Seals or packing means 78 and 80 are provided between piston 44A and cylinder 46A to isolate annular space 76 from influence from either the mud pressure P or the control pressure acting on the end of piston 44A. The control fluid is provided through connection 82 to act on the driven end of piston valve 44A. It will be noted that the areas are such that the pressure of the control fluid entering port 82 can be set at the value desired for the mud pressure P and it will maintain the pressure at that point.

Attention is next directed to FIG. 4 and FIG. which show another modification of this invention. Shown thereon is housing 84 having inlet extension 94, control fluid inlet port 100 in end member 98 and outlet port 95 at 90 to the main bore 87 which extends from inlet 94 to end member 98. Piston 88 is centered within the bore of housing 84 by centralizers 88. Valve piston 86 has head 90 made of a hard metal and Wedge shaped similar to the heads of the embodiments of FIGS. 2 and"3. A hard metal seat 92 for valve head 90 is provided in member 94 and is held in place by ring member 96 in a conventional manner. The bore of housing 84 between seat 98 and outlet 95 is considerably larger than piston 86. This permits solid particles such as cuttings to flow easily to outlet 95. This clearance 87 is made as large as necessary to accommodate solid particles passing by valve head 90 when in its greatest open position.

A sealing contact is made between piston 86 and housing 84 on the opposite side from outlet 95 from valve piston head 90. This sealing means includes packing 102, packing housing 104, which is held in place by end member 98 which is threadably connected into the end of housing 84. Control fluid is directed into control chamber 99 through port 100. The valve in FIG. 4 is illustrated in its closed position. In its open position the valve piston 86 is moved toward plate 98 when the force of the fluid striking valve head 90 being greater than the control fluid in chamber 99. This causes valve head 90 to unseat from valve seat 92 thus permitting fluid to escape in the passage between centralizers 88 and escape through outlet 95. The valve piston modification of FIG. 3 can be used to modify the device of FIG. 4.

Although the embodiments of this invention described above have been set forth in detail, it is possible to provide other modifications without departing from the spirit or inventive concept thereof.

We claim:

1. A drilling fluid control valve which comprises:

a housing member having a longitudinal bore therethrough and a lateral outlet intermediate the ends thereof;

an annular seat made of a hard metal and held within the bore of said housing and adjacent one end thereof, the internal diameter of said seat being less than the diameter of said bore;

radially spaced apart longitudinal centralizer means Within said bore and located between said annular seat and one side of said outlet and defining a plurality of flow passages between the inlet and outlet;

a piston valve mounted within said bore and centered by said centralizer means, one end of said valve piston comprising a head of hard metal, the external diameter of said head being less than the internal diameter of said seat for sealing fit within said seat, the other end of said piston valve forming a fluid pressure responsive area;

means sealing the bore between said valve piston and the inner wall of said housing so that said valve piston may sealingly slide with respect to said sealing means, said sealing means being on the other side of said outlet from said centralizer means;

the piston valve being of uniform diameter from such sealing means to and including said head of hard metal;

enclosure means enclosing the end of said housing opposite said seat means, said closure means having a port therein for the introduction of fluid to control said valve piston.

2. A valve as defined in claim 1 including a lining of hard metal within the interior of said body member and in which the face of said head of hard metal is wedge shaped and each plane of the face makes an angle of with the axis of said valve piston.

References Cited UNITED STATES PATENTS 2,731,031 1/1956 Newhouse 251324X 3,243,156 3 1966 Shoemaker .25163 3,429,385 2/1969 Jones et al. --218 X 2,084,397 6/ 1937 Hildebrandt 251324 XR 2,716,421 8/ 1955 Bertrand .251-368 XR 2,741,262 4/1956 Crookston 137539 XR WILLIAM F. ODEA, Primary Examiner RICHARD GERARD, Assistant Examiner U.S. Cl. X.R. 

